WO2007104539A1

WO2007104539A1 - Mechanico-hydraulic drive comprising a power split transmission

Info

Publication number: WO2007104539A1
Application number: PCT/EP2007/002214
Authority: WO
Inventors: Matthias Müller; Steffen Mutschler
Original assignee: Bosch Rexroth Ag
Priority date: 2006-03-13
Filing date: 2007-03-13
Publication date: 2007-09-20
Also published as: CN101321642A; US20090036248A1; EP1993866A1

Abstract

The invention relates to a drive comprising a power split transmission (1). Said power split transmission (1) comprises a hydraulic pump (9) and a hydraulic engine (12) which are interconnected via a first working line (10) and a second working line (11). The drive also comprises at least one first storage element (21) for storing braking energy, the at least one first storage element (21) being linkable to the first working line (10) or the second working line (11). The hydraulic pump (9) and the hydraulic engine (12) are mechanically connected to an output shaft (18).

Description

MECHANICAL-HYDRAULIC DRIVE WITH A POWER BRANCH

The invention relates to a drive with a

Power split transmission and a storage element for storing braking energy.

Drive systems for commercial vehicles are frequently used in which two drive trains are driven by means of a primary drive motor. On the one hand, a mechanical drive is used and in a second branch, a hydrostatic drive. In the hydrostatic drive, a hydraulic pump and a hydraulic motor cooperate with the hydraulic motor with the

Travel drive is connectable. Such a drive system is proposed in US 4,215,545. There, an output shaft of a primary drive motor via two clutches with a mechanical branch or a hydraulic pump can be connected. The hydraulic pump can be connected to a hydraulic motor via a first working line and a second working line. In order to allow a reversal of the flow direction, a distribution valve is provided which can interchange the connections between the hydraulic motor and the hydraulic pump. For recovering energy after a braking operation, a storage element can be connected to one of the two working lines via a switching valve. For storing and recovering energy, the storage element is connected to the one working line. During the braking operation, the distribution valve is switched so that the hydraulic motor acting as a pump promotes pressure medium in the storage element. To recover the energy is from the Memory element taken over the switching valve pressure medium and fed to the hydraulic motor.

In the described drive system, it is disadvantageous that only the hydraulic motor is used for storing energy. Furthermore, the additional distribution valve is required by the connection of the storage element with only one of the working lines via the switching valve to connect the corresponding port of the hydraulic motor with the storage element can.

The invention has for its object to provide a drive with a power split transmission, in which an improved recovery of kinetic energy during braking is possible and in which a switch between the terminals of the hydraulic pump and the hydraulic motor is not required.

The object is achieved by the drive according to the invention with the features of claim 1.

The drive according to the invention according to claim 1 comprises a power split transmission, which comprises a hydraulic pump and a hydraulic motor. The hydraulic pump and the hydraulic motor are connected to each other via a first working line and a second working line. The hydraulic pump and the hydraulic motor together with the first and the second working line form a closed hydraulic circuit. The closed hydraulic circuit forms a first branch of the power split transmission. For spoking kinetic energy during a braking operation, a first storage element with the first working line or the second working line connectable. Through the connection of the first storage element with the first or the second working line, the connections between the hydraulic pump and the hydraulic motor can always remain unchanged, since the respective pressurized by the hydraulic motor or by the hydraulic pump during the braking process working line with the first storage element is connectable , The hydraulic motor and the hydraulic pump are each mechanically connected to an output shaft.

In the dependent claims advantageous refinements of the drive according to the invention are carried out.

According to a preferred embodiment, the hydraulic motor is connected via a mechanical transmission with the output shaft of the power split transmission. The mechanical transmission according to the invention comprises at least a first planetary gear. An element, e.g. B. the ring gear of the first planetary gear is doing with the first

Hydraulic motor connected and another element, e.g. the sun gear, the first planetary gear is connected to the hydraulic pump. By coupling an element with the hydraulic motor and at the same time another element of the planetary gear with the hydraulic pump, it is possible to convert the kinetic energy into pressure energy both by means of the hydraulic motor and by means of the hydraulic pump in the sliding or braking operation and thus by storage in the first Storage element for recovery available.

Furthermore, it is advantageous if the power split transmission comprises a mechanical power branch a hydraulic power branch and the two power branches can be operated jointly or independently of each other.

In particular, it is advantageous to provide a coupling with which the drive motor of the

Power split transmission is uncoupled. In the case of the recovery of kinetic energy is then the complete, in the drive train due to the inertia attributed braking energy by the hydraulic motor and the hydraulic pump together in the form of

Pressure energy stored in the first memory element. If this braking effect does not suffice, the drive motor can also be connected to the power split transmission by engaging the clutch. Is in addition the drive motor with the

Connected power split transmission, so its braking power can also be used and the total braking power wereden increased.

Furthermore, it is advantageous in the

Power split transmission to provide a first drive shaft portion and a second drive shaft portion, which together form the drive shaft of the power split transmission. The drive shaft portion is connected to the hydraulic pump and the second drive shaft portion is connected to the sun gear of the first planetary gear. The connection between the first drive shaft section and the second drive shaft section is detachable, whereby the hydraulic pump from the sun gear of the first

Planet gear can be decoupled. Such an arrangement has the advantage that the sole use of the hydrostatic branch of the power split transmission is possible. In this case the drive motor is only connected to the hydraulic pump via the first drive shaft section.

According to a further advantageous embodiment, the power split transmission comprises a second planetary gear. The second planetary gear also has a sun gear and a ring gear, wherein the ring gear of the first planetary gear is connected to the ring gear of the second planetary gear. Thus, both ring gears of the two planetary gear are connected together with the hydraulic motor. The two sun gears are also connected to each other, since both the sun gear of the first planetary gear and the sun gear of the second planetary gear are connected to the second drive shaft.

Such an arrangement makes it possible to decouple the first drive shaft section from the second drive shaft section and to realize a purely hydrostatic drive. In this case, the different ratios of the planetary gear can be selected so that in contrast to the drive over both branches of the power split transmission, a lower speed range is covered. In order to achieve a corresponding input speed for the planetary gear when using both branches of the power split transmission, it is particularly advantageous to connect the first drive shaft section and the second drive shaft section via a gear stage with each other. The web of the second planetary gear is blocked. The web of the first planetary gear is connected to an output shaft of the power split transmission.

During storage or recovery of the stored kinetic energy, the first storage element is connected to the first or the second working line. The drive preferably has a second storage element, which is connected during the storage process or the recovery of energy with the respective other working line. The hydraulic motor is connected to the hydraulic pump in the manner already mentioned in a closed hydrostatic circuit. By storing or recovering kinetic energy it comes to a

Pressure medium removal or a return of pressure medium from the circulation or into the circulation. This volume flow is compensated by the second storage element, wherein the compensation takes place respectively on the low pressure side. In particular, it is advantageous to design the first memory as a high-pressure accumulator and the second accumulator as a low-pressure accumulator. In this case, it may furthermore be particularly advantageous to connect a storage pressure holding device with a pressure holding valve upstream of the high-pressure accumulator. Such a memory pressure retaining device prevents the unintentional complete emptying of the first memory element.

It is also preferred if, during braking operation, the drive motor is switched off above a pressure limit value in the first storage element. Advantageous embodiments are illustrated in the drawing and are explained in more detail in the following description. Show it:

1 shows a first embodiment of a drive according to the invention,

2 shows a second embodiment of a drive according to the invention,

Fig. 3 shows a first embodiment of a

Valve block,

4 shows a second embodiment of a valve block,

5 shows a third embodiment of a valve block.

6 shows a fourth embodiment of a valve block; and

Fig. 7 shows a third embodiment of a drive according to the invention with control components.

In Fig. 1, a first embodiment of a drive according to the invention is shown. A power split transmission 1 comprises a drive motor 2 through which a driven axle 3, for example a wheel loader, is driven. In the illustrated embodiment, this is a single vehicle axle 3. However, it is just as well through the power split transmission 1 a Transfer case of a four-wheel drive drivable. The driven axle 3 has a differential 4 through which the vehicle wheels are driven.

The drive motor 2 can be connected to a drive shaft 5, by means of which the torque generated by the drive motor 2 is fed to the power split transmission 1. Via a first gear 6, a hydraulic pump 9 is connected to the drive shaft 5. The first gear stage 6 has a first spur gear 7 and a second spur gear 8. The first spur gear 7 and the second spur gear 8 are in permanent engagement with each other, so that the drive shaft 5 is permanently connected to the hydraulic pump 9.

The hydraulic pump 9 is designed to convey pressure medium in two directions and is adjustable in its delivery volume. The adjustment of the hydraulic pump 9 is effected by an adjusting device, not shown, which is preferably controlled by an electronic control unit.

To the hydraulic pump 9, a first working line 10 and a second working line 11 is connected. Through the first working line 10 and the second working line 11, a hydraulic motor 12 is connected to the hydraulic pump 9. The hydraulic motor 12 is also designed for two flow directions and also adjustable in its displacement. The hydraulic pump 9 forms together with the hydraulic motor 12 and the first and the second

Working line 10, 11 a closed hydraulic circuit. The hydraulic pump 9 and the hydraulic motor 12 are preferably designed as axial piston machines. For example, swash plate or oblique axis machines can be used.

The hydraulic motor 12 is connected via a hydraulic motor output shaft 28 with a third spur gear 29. About the third spur gear 29 of the hydraulic motor 12 acts with a mechanical drive, in the illustrated embodiment, a first planetary gear 13 together. The first planetary gear 13 has a sun gear 14 and a ring gear 15. Furthermore, the first planetary gear 13 comprises a web 16, on which a plurality of planet gears 17.1, 17.2 are arranged and rotatably mounted thereon. The web 16 of the first planetary gear 13 is connected to an output shaft 18 and transmits its output torque via a second gear stage 19 to a differential input shaft 20 to the driven axle 3 of the vehicle. The connection of the hydraulic pump 9 and the hydraulic motor 12 with the sun gear 14 and the ring gear 15 is merely exemplary. Depending on the desired transmission ratio, the elements of the planetary gear 13 (sun 14, ring gear 15 and land 16) can also be assigned differently. In any case, there is a mechanical connection of both the hydraulic pump 9 and the hydraulic motor 12 with the output shaft 18 and the drive train of the vehicle.

During driving, the drive shaft 5 is driven by the drive motor 2. With the drive shaft 5, the sun gear 14 of the first planetary gear 13 is connected. At the same time via the first gear 6, the hydraulic pump 9 and in response to the set flow rate or from the set displacement of the hydraulic motor. 12, the hydraulic motor output shaft 28 is driven. This is by the Hydromotor output shaft 28, the third spur gear 29 is driven, which is in engagement with a toothing 30 arranged externally on the ring gear 15 of the first planetary gear 13. Both the sun gear 14 and the ring gear 15 of the first planetary gear 13 are thus either directly by the drive motor 2 or via the hydrostatic branch of the

Power split transmission 1 driven. This leads to a resulting rotational movement of the web 16, which is transmitted via the output shaft 18, the second gear stage 19 and the differential input shaft 20 to the driven axle 3 of the vehicle. In the illustrated embodiment of the power split transmission 1 power is transmitted to the driven axle 3 both via the hydrostatic branch and via the mechanical branch.

If the vehicle is in coasting mode, then the power flow reverses and due to the inertia of the vehicle, a torque is now fed from the driven axle 3 from. About the first planetary gear 13 is now driven by the web 16, the ring gear 15 and the sun gear 14. Due to the permanent coupling between the drive shaft 5 and the hydraulic pump 9 thereby both the hydraulic motor 12 and the hydraulic pump 9 is driven. In order to use the released kinetic energy as completely as possible, a clutch 31 is provided with which the drive motor 2 can be decoupled from the drive shaft 5. The coupling 31 can, for example, as

Single-disc dry clutch be executed. In order to store the braking power, so the released kinetic energy of the vehicle, at least one memory element is provided. The memory element is in the Furthermore, a second hydraulic accumulator 22 is provided as a further memory element. The first hydraulic accumulator 21 is preferably designed as a high-pressure accumulator. By contrast, the second hydraulic accumulator 22 is designed as a low-pressure accumulator and provided to compensate for the added or removed volume flow.

In order to connect the first hydraulic accumulator 21 and the second hydraulic accumulator 22 to the first working line 10 and the second working line 11, a valve block 23 is provided. The valve block 23 is connected via a first connecting line 24 to the first working line 10. In addition, the valve block 23 is connected via a second connecting line 25 to the second working line 11. The first hydraulic accumulator 21 is connected to the valve block 23 via a high-pressure accumulator line 16, while the second hydraulic accumulator 22 is connected to the valve block 23 via a low-pressure accumulator line 27. Embodiments for the valve block 23 will be explained below in detail with reference to FIGS. 3-6.

Depending on the respective direction of travel, pressure medium is conveyed either clockwise or counterclockwise in the hydrostatic circuit. For the following statements it is assumed that a promotion of pressure medium takes place in a clockwise direction. This is described below as forward drive. In such a forward drive pressure medium is thus promoted by the hydraulic pump 9 in the first working line 10 and relaxed via the hydraulic motor 12 in the second working line 11 during a normal drive. If the vehicle is now in coasting mode or if it should be braked, then the pressure conditions are reversed. The hydraulic motor 12 now acts as a pump and promotes by increasing the pressure pressure medium in the second working line eleventh

By adjusting the adjustment of the hydraulic pump 9 can also be achieved that the driven via the drive shaft 5 hydraulic pump 9 reverses its conveying direction and thus also promotes pressure medium in the second working line 11. That of the hydraulic pump 9 and the hydraulic motor 12 in the second

Working line 11 conveyed pressure medium is supplied to the first hydraulic accumulator 21. For this purpose, the valve block 23, the second connecting line 25 is connected to the high-pressure accumulator line 26. From the second working line 11 pressure medium, which under high

Pressure is conveyed via the second connecting line 25 and the high-pressure accumulator line 26 into the first hydraulic accumulator 21. At the same time, the second hydraulic accumulator 22 is connected to the first working line 10 through the valve block. For this purpose, the low-pressure accumulator line 27 is connected to the first connecting line 24 in the valve block 23. The pumped into the first hydraulic accumulator 21 pressure medium is thus removed from the second hydraulic accumulator 22. Both the hydraulic pump 9 and the hydraulic motor 12 suck from the first working line 10 pressure medium and convey it to the second working line 11, from which it is stored by increasing the local pressure in the first hydraulic accumulator 21.

If the braking power due to the increase of the pressure in the first hydraulic accumulator 21 is not sufficient, the drive shaft 5 can additionally be supported on the drive motor 2. In this case, the connection remains exist between the drive motor 2 and the drive shaft 5 by the clutch 31 is not disengaged.

In order to recover the braking energy or the kinetic energy of the vehicle stored in the form of pressure energy in the first hydraulic accumulator 21, the pressure medium from the first hydraulic accumulator 21 is returned to the hydrostatic circuit. If an acceleration in the forward direction, the high-pressure accumulator line 26 is connected to the first through the valve block 23

Connecting line 24 connected. Thus, the stored in the first hydraulic accumulator 21 pressure fluid of the first working line 10 is supplied. The return of the pressure energy is simultaneously possible via the hydraulic pump 9 and via the hydraulic motor 12. Thus, both the hydraulic pump 9 and the hydraulic motor 12 can be acted upon by the first working line 10 with pressure medium, so that both the hydraulic pump 9 and the hydraulic motor 12 act as a motor and transmit torque to the drive shaft 5 and the hydraulic motor output shaft 28. The torque generated by the hydraulic pump 9 thus supports the transmitted from the drive motor 2 to the drive shaft 5 torque. It is also possible to set the hydraulic pump 9 to vanishing delivery volume. Thus, the entire pressure energy stored in the first hydraulic accumulator 21 is returned directly via the hydraulic motor 12.

While the removal of pressure medium from the first hydraulic accumulator 21 via the first working line 10, the second hydraulic accumulator 22 is connected to the second working line 11. For this purpose, the valve block 23 connects the second connecting line 25 with the low-pressure accumulator line 27. Das aus Hydraulic accumulator 21 recirculated pressure medium is thus discharged to the volume compensation in the second hydraulic accumulator 22.

By recovering the kinetic energy of the vehicle, which is released during the braking process, results in a lower fuel consumption and a reduced brake wear during operation of the vehicle. Such an arrangement is particularly advantageous in vehicles which frequently undergo acceleration and braking cycles. Such vehicles are, for example, wheel loaders or garbage collectors. The arrangement according to the invention, in which the first hydraulic accumulator 21 can be connected alternately to the first working line or the second working line 10 or 11, has the advantage that the hydraulic motor 12 does not have to be pivoted beyond its zero position. The flow direction through the hydraulic motor 12 can thus be maintained at the transition from a drive to the push mode. This leads to an increase in the stability of the driving state. Furthermore, there is an increased power available when restarting, since in addition to the power of the drive motor 2, the stored energy can be used to accelerate the vehicle.

2, a second embodiment of the drive according to the invention is shown. Those elements that correspond to the elements of Fig. 1 are provided with identical reference numerals. A general, repeated description is omitted to avoid repetition. The mechanical transmission in the second embodiment has, in addition to the first planetary gear 13, a second planetary gear 32. The second planetary gear 32 comprises a ring gear 33 and a sun gear 34. Between the ring gear 33 and the sun gear 34 of the second planetary gear 32 planetary gears 37.1 and 37.2 are arranged, which are rotatably fixed to a web 35. The web 35 can be blocked by means of a blocking device 36. In the illustrated embodiment, the ring gear 15 of the first planetary gear 13 and the ring gear 33 of the second planetary gear 32 are connected to a common ring gear. The toothing 30 'is arranged in the region of the ring gear 33 of the second planetary gear 32. About the teeth 30 'of the hydraulic motor 12 with the common ring gear 15, 33 of the first planetary gear 13 and the second planetary gear 32 is connected. The planetary gear 13 and 32 have different gear ratios.

The drive shaft of the power split transmission 1 'of FIG. 2 is divided into two and comprises a first drive shaft section 5.1 and a second drive shaft section 5.2. The second

Drive shaft section 5.2 is fixedly connected to the sun gear 14 of the first planetary gear 13 and the sun gear 34 of the second planetary gear 32. The first drive shaft section 5.1 is releasably connected to the drive motor 2, wherein for releasable connection here also a coupling 31 is provided. Also connected to the first drive shaft section 5.1 is the first gear stage 6, which couples the hydraulic pump 9 to the first drive shaft section 5.1.

For connecting the first drive shaft section 5.1 to the second drive shaft section 5.2, a third gear stage 38 or a fourth gear stage 39 is provided. The third gear stage 38 includes a fourth, fifth and sixth spur gear 40, 41 and 42. The sixth spur gear 42 is permanently connected to the second drive shaft section 5.2. The fifth spur gear 41 is connected to an intermediate shaft 43. The fourth spur gear 40 is detachably connected to the first drive shaft section 5.1.

For fixed connection of the fourth spur gear 40 with the first drive shaft section 5.1, a second clutch 48 is provided. The second clutch 48 may be designed either as the clutch 31 as a friction clutch or be a positive clutch. The third gear stage 38 is provided for example for forward travel. The fourth gear stage 39, on the other hand, is used to generate the same

Gear ratio used in reverse. The fourth gear stage has a seventh, an eighth and a ninth spur gear 44, 45 and 46, which also like the fourth to sixth spur gears 40 - 42 are in permanent engagement with each other. The seventh spur gear 44 is detachably connected to a direction reversal 47. The eighth spur gear 45 is connected to the intermediate shaft 43 and thus to the fifth spur gear 41. The fourth gear stage 39 is completed by the ninth spur gear 46, which with the second

Drive shaft section 5.2 is firmly connected. For a forward drive, in which in addition to the hydrostatic branch and the mechanical branch is used for driving, the second clutch 48 is closed, while the third clutch 49 is opened. For a reverse drive with both the mechanical branch and the hydrostatic branch, the second clutch 48 is opened and the third clutch 49 is closed. The direction of rotation reversal 47 has a gear pair, whereby the direction of rotation of the seventh spur gear 44 with respect to the direction of rotation of the fourth spur gear 40 is reversed. To achieve the same driving speed ranges in forward and

Reverse direction, the ratios of the third gear stage 38 and the fourth gear stage 39 are preferably identical.

In the embodiment of Fig. 2, it is also possible to use a driving range in which only the hydrostatic branch is used. In such a driving operation, both the second clutch 48 and the third clutch 49 are opened. At the same time, the blocking device 36 is actuated. The

Blocking device 36 may for example be a positive coupling with which the web 35 of the second planetary gear 32 is fixed to the housing side.

Due to the different ratios of the first planetary gear 13 and the second planetary gear 32 results in a torque introduction by the hydraulic motor 12 via the hydraulic motor output shaft 28 and the associated third spur gear 29 to the ring gears 15, 33 of the first

Planetary gear 13 and the second planetary gear 32, a rotation of the web 16 of the first planetary gear 13 and thus a torque on the output shaft 18th

Is the vehicle in this

Driving speed range in which a drive only via the hydrostatic branch of

Leistungsverzweigungsgetriebes 1 ', in a braking operation, a brake energy recovery due to the missing connection between the first drive shaft section 5.1 and the second drive shaft section 5.2 exclusively via the hydraulic motor 12 done. Without swinging through the hydraulic motor 12, a pressure is generated in the downstream working line by the now acting as a pump hydraulic motor 12, which can be stored in the first hydraulic accumulator 21. In order to enable a storage of released kinetic energy, preferably the hydraulic pump 9 to vanishing

Delivery volume. In the case of a forward drive, the hydraulic motor 12 in the second working line 11, which is located downstream of the hydraulic motor, a pressure and the valve block 23 connects the second connecting line 25 with the high-pressure accumulator line 26. As a result, while increasing the pressure in the first hydraulic accumulator 21 kinetic Energy stored in the form of pressure energy in the first hydraulic accumulator 21. In the manner already described, the low-pressure accumulator line 27 is simultaneously connected by the valve block 23 to the first connecting line 24, so that a volume flow compensation by the second hydraulic accumulator 22 can take place.

In the second vehicle speed range, the

Blocking device 36 is not used and the web 35 of the second planetary gear 32 can rotate freely. At the same time, the second clutch 48 is engaged during forward travel and thus connects the first drive shaft section 5.1 with the second

Drive shaft section 5.2. Due to the use of an intermediate shaft 43, the directions of rotation of the first drive shaft section 5.1 and of the second drive shaft section 5.2 correspond to one another. The function is in this Switching state identical to the already described with reference to FIG. 1 function with a direct connection of the sun gear 14 of the first planetary gear 13 to the drive motor 2. In the illustrated embodiment of FIG. 2, it is therefore also possible in the second driving range, the released kinetic energy by conveying pressure medium by the hydraulic pump 9 and at the same time by the hydraulic motor 12 in the first hydraulic accumulator 21 to store. Likewise, the recovery of the stored energy can be done either via the hydraulic motor 12 alone or both via the hydraulic motor 12 and via the hydraulic pump 9. For the exclusive generation of a braking effect by storing the released kinetic energy is also here by the clutch 31 of the first

Drive shaft section 5.1 separable from the drive motor 2.

All operating situations, which have been explained above exclusively for the forward drive with a promotion of hydrostatic pressure medium in the clockwise direction of the hydraulic circuit, apply in a similar manner to reverse. In the exemplary embodiment of FIG. 2, it should merely be noted that in the second driving range, the second clutch 48 is opened and the third clutch 49 is closed. In contrast to the preceding description when driving forward, the pressure conditions in the first and the second working line reverse and the first working line 10 becomes to the hydraulic motor 12 downstream working line, which is to be connected to the first hydraulic accumulator 21 for storing energy. When recovering the stored energy, it is also possible to reverse the direction of travel at the same time. That is, by the valve block 23, the pressure medium stored in the first hydraulic accumulator 21 can also be returned to that working line from which it was removed for storage. If, for example, a vehicle is first braked to zero during a forward drive, an acceleration in the reverse direction can be achieved from standstill by returning the pressure medium to the second working line 11.

Detailed embodiments of the valve block 23 for connecting the two hydraulic accumulators 21, 22 with the working lines 10, 11 are shown in FIGS. 3-6.

A first, simple exemplary embodiment of a valve block 23 is shown in FIG. 3. For connecting the first connecting line 24 to the high-pressure accumulator line 26 or the low-pressure accumulator line 27 or the second connecting line 25 to the high-pressure accumulator line 26 or the low-pressure accumulator line 27, the valve block 23 comprises a directional control valve 51

Directional control valve 51 is a 4/3-way valve. In a neutral position 52 all four ports of the directional control valve 51 are separated from each other. There is thus no through-flow connection between the high pressure accumulator line 26 and the

Low-pressure accumulator line 27 and the two connecting lines 24 and 25 is in this switching state of the directional control valve 51 already pressure medium stored in the first hydraulic accumulator 21, so is due to the complete decoupling of the hydrostatic circuit longer-term storage of pressure medium possible. Leakage is prevented by this separation.

From the neutral position 52, the directional control valve 51 can be brought into a first shift position 53 or a second shift position 54. In the first switching position 53, the first connecting line 24 is connected to the low-pressure storage line 27 and the second connecting line 25 to the high-pressure accumulator line 26. In contrast, in the second switching position 54, the first connecting line 24 is connected to the high-pressure accumulator line 26 and the second connecting line 25 to the low-pressure accumulator line 27. The directional control valve 51 is brought to its first shift position 53 during a braking operation in the forward direction. Forward acceleration is possible when the directional control valve 51 is in its second shift position 54. In reverse braking and forward acceleration accordingly the opposite switching positions are taken. In order to ensure a return of the directional control valve 51 in its neutral position, a first centering spring 55 and a second centering spring 56 is provided. Similar to the first centering spring 55, a first solenoid 57 acts as an actuator for actuating the directional control valve 51 on the directional control valve 51. Upon actuation of the first solenoid 57, the directional control valve 51 is out of its neutral position 52 against the force of the counteracting second centering spring 56 in its first Switching position 53 brought. Accordingly, upon actuation of a second solenoid 58, the Directional control valve 51 brought into its second switching position 54 under compression of the first centering spring 5. Instead of the first and second electromagnets 57, 58 used in the illustrated embodiment as actuators, other actuators can be used. For example, the generation of a hydraulic force at corresponding measuring surfaces of the directional control valve 51 is conceivable.

Preferably, the first hydraulic accumulator 21 is preceded by a storage pressure maintaining device 59. To advance the accumulator pressure holding device 59, this is preferably arranged in the high-pressure accumulator line 26 within the valve block 23. In the memory pressure holding device 59 branches the

High-pressure accumulator line 26 in a first leg 26 'and a second leg 26' '. The line branches 26 'and 26' 'are arranged parallel to each other. In the first line branch 26 ', a pressure relief valve 60 is arranged as a pressure holding valve, which is acted upon by a spring 61 in the closing direction. Opposing to the force of the closing spring 61, the pressure prevailing in the first hydraulic accumulator 21, which is supplied to a measuring surface via a measuring line 62, acts. This is an opening of the

.Druckbegrenzungsventils 60 only possible if the pressure prevailing in the first hydraulic accumulator 21 exceeds a value set by the closing spring 61.

A check valve 63, which opens in the direction of the first hydraulic accumulator 61, is arranged in the second line branch 26 "'arranged parallel thereto. A supply of pressure medium into the first hydraulic accumulator 21 is therefore always independent of the prevailing pressure there possible. The storage pressure retaining device 59 thus ensures that there is always a certain minimum pressure in the first hydraulic accumulator 21 and that complete removal of pressure medium from the first hydraulic accumulator 21 is not possible.

The control of the first and second electromagnets 57, 58 is preferably carried out via an electronic control unit, which controls the switching of the electromagnets 57 and 58 starting from the selected direction of travel.

A second embodiment of a valve block 23 is shown in FIG. 4. In the embodiment of a valve block 23 shown in FIG

Connection between the first connecting line 24 and the second connecting line 25 and the high-pressure accumulator line 26 and the low-pressure accumulator line 27 by means of a first to fourth seat valve 64, 65, 66 and 67. The four

Poppet valves 64-67 are preferably constructed the same. In order to avoid unnecessary repetition, only the construction of the first seat valve 64 will be described in detail below. For clarity, therefore, the reference numerals of the individual elements of the seat valves are arranged only on the first seat valve 64.

The first seat valve 64 has a closing body 68, by means of which a first and a second pressure chamber are separated from one another in a closed position of the first seat valve 64. On the closing body 68, a first surface 69 in the first pressure chamber and a second, in the same direction oriented surface 70 is formed in the second pressure chamber. In opposite Direction oriented is a third surface 71. The three surfaces 69 - 71 are each acted upon by a pressure. Similar to the force acting on the third surface 71 hydraulic force of the closing body 68 is acted upon by the force of a first valve spring 78. The first valve spring 78 acts on the first seat valve 64 in the closing direction.

Accordingly, a valve spring 79 - 81 are also arranged on the second to fourth seat valves 65 - 67, which act on the respective seat valve 65 - 67 in the closing direction.

The second pressure chambers of the first seat valve 64 and the third seat valve 66 are via a first

Valve connecting line 72 connected to each other. Likewise, the second pressure chambers of the second seat valve 65 and the fourth seat valve 67 are connected to each other via a second valve connecting line 73.

The first pressure chamber of the first seat valve 64 is connected to the second connection line 25 via a first valve connection line 74. In the closed state of the first seat valve 64, the first valve connection line 74 is from the first

Valve connecting line 72 separated. The first pressure chamber of the second seat valve 65 is connected to the first connection line 25 via a second valve connection line 75. The first connection line 24 is via a third

Valve connecting line 76 to the first pressure chamber of the third seat valve 66 and connected via a fourth valve connection line 67 to the first pressure chamber of the fourth seat valve 67. The first valve connecting line 72 is connected to the first hydraulic accumulator 21 via the high-pressure accumulator line 26. The second valve connecting line 73 is connected to the second hydraulic accumulator 22 via the low-pressure accumulator line 27.

As already stated, the closing bodies of the seat valves 64-67 are acted upon via a respective valve spring 78-81 in the direction of their closed position. Provided on the respective third surfaces of the seat valves 64

- 67 does not act hydraulic force, the force of the valve springs 78 - 81 is not sufficient to keep the poppet valves 64 - 67 in its closed position. The hydraulic forces acting on the first surface and the second surface of the poppet valve 64-67 exceed the force of the closing valve spring 78

- 81.

In order to keep the poppet valves 64-67 in their respective closed position, therefore, a hydraulic force is generated on the respective third surface. To generate the hydraulic force, the third surface 71 of the first seat valve 64 can be acted upon by a control pressure via a first control pressure line 82. Likewise, the third surface of the second seat valve 65 via a second control pressure line 83, the third surface of the third seat valve 66 via a third control pressure line 84 and the third surface of the fourth seat valve 67 via a fourth control pressure line 85 with a control pressure acted upon. The first control pressure line 82 and the fourth control pressure line 85 are jointly supplied via a first line section 76 of the control pressure. Likewise, the second control pressure line 83 and the third control pressure line 84 is supplied together via a second line section 87, a control pressure. For generating or for assigning the control pressure to the first line section 86 and the second line section 87, a pilot valve 88 is provided.

The pilot valve 88 connects depending on its switching position, the first line section 86 and / or the second line section 87 with a maximum pressure line 89. The maximum pressure line 89 is supplied by a maximum pressure selector 90 of the highest available in the system pressure.

For this purpose, the maximum pressure selection device 90 has a first changeover valve 91 and a second changeover valve 92. The two shuttle valves 91, 92 are connected to each other via a shuttle valve connection line 93. The shuttle valve connection line 93 is connected via a high-pressure accumulator line branch 94 to the first valve connection line 72 and thus to the first hydraulic accumulator 21 via the high-pressure accumulator line 26. The pressure prevailing in the first hydraulic accumulator 21 is thus applied to the respective inputs of the first shuttle valve 91 and of the second shuttle valve 92. Another input port of the first

Shuttle valve 91 is connected via a first supply line 95 to the second connecting line 25. A second input terminal of the second shuttle valve 92 is connected to the first connection line 24 via a second supply line 96. By the first

Shuttle valve 91 is a comparison of the prevailing pressure in the second connecting line 25 with the pressure prevailing in the first hydraulic accumulator 21 pressure. At the same time by the second shuttle valve 92 a Pressure comparison between the pressure in the first connecting line 24 and the first hydraulic accumulator 21 performed. The higher of the two pressures is output by the first shuttle valve 91 and the second shuttle valve 92 at their output ports. The output terminals of the first shuttle valve 91 and the second shuttle valve 92 are connected to each other via an output connection line 97. In the output connection line 97, a first check valve 98 and a second check valve 99 are arranged, wherein the opening direction of the two check valves 98, 99 directed towards each other. Between the two check valves 98, 99, the maximum pressure line 89 is connected to the output connection line 97.

The pilot valve 88 is a 3/3-way valve, which is acted upon by a pilot valve spring 100 in the direction of a first switching position 102. The pilot valve 88 has a second shift position 103 and a third

Switching position 104 on. To bring the pilot valve 88 from its first shift position 102 to the second shift position 103 and the third shift position 104, an electromagnet 101 is provided as the actuator. The solenoid 101 acts on the pilot valve 88 against the force of the pilot valve spring 100. In dependence on the force generated by the solenoid 101, the pilot valve is brought into its second switching position 103 or into its third switching position 104. If no control signal is applied to the electromagnet 101, the pilot valve 88 is brought back into its first switching position 102 by the force of the pilot valve spring 100. In the first switching position 102, the pilot valve connects the maximum pressure line 89 to both the first line section 86 and the second line section 87. Thus, the first control pressure line 82 and the second control pressure line 85 are pressurized with the highest system pressure via the first line section 86. Likewise, the highest system pressure is supplied as control pressure via the second line section 87 of the second control pressure line 83 and the third control pressure line 84. In the first

Switching position of the pilot valve 88, therefore, all the poppet valves 64 - 67 acted upon by a control pressure corresponding to the highest system pressure on the first to fourth control pressure line 82 - 85. Regardless of the hydraulic forces acting in the opposite direction on the first and second surfaces of the poppet valve 64-67, therefore, the poppet valves 64-67 are held in their closed position.

If, however, the pilot valve 88 by energizing the

Electromagnet 101 brought into its second switching position 103, so only the first line section 86 is connected to the maximum pressure line 89. As a result, the third surfaces of the first seat valve 64 and the fourth seat valve 85 are subjected to a control pressure and held in their closed position. In a manner not shown, the third surfaces of the second seat valve 65 and the third seat valve 66 are relaxed, so that due to the oppositely directed hydraulic forces, the second seat valve 65 and the third seat valve 66 are brought into their open position. By adjusting the second seat valve 65 in the direction of its open position, the second valve connecting line 73 with the second Valve connection line 75 connected throughflow. As a result, the second connection line 25 is connected to the low-pressure storage line 27 via the second seat valve 65. At the same time, the third seat valve 66 is brought into its open position, in which the first valve connection line 72 is connected to the third valve connection line 76. The first connecting line 24 is thus connected to the high-pressure accumulator line 26 via the third seat valve 66. Consequently, in the first switching position 103, the first

Hydraulic accumulator 21 connected to the first working line 10 and at the same time the second hydraulic accumulator 22 to the second working line 11th

To use the various connection possibilities of the working lines 10, 11 with the first or second hydraulic accumulator 21, 22, reference is made to the above statements. If the pilot valve 88 is brought into its third switching position 104, so in contrast to the second switching position 103 of the second

Line section 87 connected to the maximum pressure line 89. In this position, the second control pressure line 83 and the third control pressure line 84 is supplied with the control pressure and the second and third seat valves 65, 66 held in the closed position. At the same time, the first seat valve 64 and the fourth seat valve 67 are brought into their open position. In the open position of the first seat valve 64, the first valve connection line 74 is connected to the first valve connection line 72. As a result, the second connecting line 25 is connected to the first hydraulic accumulator 21. By means of the fourth seat valve 67, in its open position, the fourth valve connection line 77 is connected to the second valve connection line 73, whereby the second hydraulic accumulator 22 is connected to the first connection line 24. In the second

Switching position of the pilot valve 88 is thus the first working line 10 with the second hydraulic accumulator 22 and the second working line 11 connected to the first hydraulic accumulator 21.

5, a further embodiment of the valve block 23 is shown. The structure corresponds substantially to that of FIG. 4, wherein a single shuttle valve 105 is used instead of the maximum pressure selector for generating and providing the highest available system pressure. The shuttle valve 105 is connected on the one hand to the high-pressure storage line branch 94 and on the other hand to a delivery pressure line 106. The delivery pressure line 106 is connected at its other end to the hydraulic pump 9 and leads the individual shuttle valve 105 to the higher pressure available in the working lines. By the single shuttle valve 105 is thus provided at its output, which is connected to the maximum pressure line 89, the highest system pressure. The comparison is made by the single shuttle valve 105 directly between the prevailing in the first hydraulic accumulator 21 pressure and the higher of the two working line pressures.

In addition, the pilot valve 88 'is supplemented by a fourth connection, which is connected via an expansion line 107 with a tank volume 108. While in the second switching position 103 of the pilot valve 88 'the maximum pressure line 89 is connected to the first line section 86, the second line section 87 is simultaneously connected to the tank volume 108 via the expansion line 107. As a result, the second seat valve 65 and the third seat valve 66 are relaxed on their respective third surface. Conversely, while the second line section 87 is connected to the maximum pressure line 89 in the third switching position 104 of the pilot valve 88 ', the first line section 86 is connected to the expansion line 107 and thus to the tank volume 108. Thereby, the third surfaces of the first seat valve 64 and the fourth seat valve 67 are relieved in the tank volume. The function corresponds to the

Function of the valve block 23 shown in FIG. 4, so that dispensing from a new description of the operation.

Another embodiment of a valve block 23 for the drive according to the invention is shown in FIG. 6. As in the embodiment of FIG. 5, the selection of the highest system pressure via a single shuttle valve 105 also takes place here. Instead of a single pilot valve 88 ', however, a first pilot valve 109 and a second pilot valve 110 are provided here. The first pilot valve 109 has a first switching position 111 and a second switching position 112. In the first switching position 111, in the direction of which the first pilot valve 109 due to the force of a compression spring

113 is held, the first line section 86 is connected to the maximum pressure line 89. Is against the force of the first compression spring 113 by a solenoid

114, the first pilot valve 109 in its second Switching position brought 112, the first line section 86 is connected to the expansion line 107.

The second pilot valve 110 also has a first one

Switching position 115 and a second switching position 116 on. In the first switching position 115, in the direction of which the second pilot valve 110 is acted upon by a second compression spring 117, the maximum pressure line 89 is connected to the second connection line 87. If, on the other hand, the second pilot valve 110 is brought into its second switching position 116 by the second switching magnet 118, then the expansion line 107 is connected to the second connecting line 87. The actuation of the two solenoids 114 and 118 takes place such that during the braking operation or during the recovery of stored energy in each case a pilot valve 109 or 110 in its first switching position 111 and 115 and the other pilot valve 110, 109 each in the other switching position 116 or 112 is located. As in the previous examples, it follows that either the first line section 86 or the second line section 87 are subjected to the control pressure. At the same time, the respective other line section 87 or 86 is connected to the expansion line 107. As a result, either the first seat valve 64 and the fourth seat valve 67 are closed and the second seat valve 65 and the third seat valve 66 open or vice versa.

FIG. 7 shows a further illustration of the drive 1 'according to the invention of FIG. 2. The drive 1 "shown in FIG. 7 comprises, in addition to the already known drive components, the control system the drive 1 '' required control components. Thus, in particular a first pressure sensor 120 is provided, which is connected via a first sensor line 121 to an electronic control unit 124. With the help of the pressure sensor 120 is in the first

Memory element 21 prevailing accumulator pressure detected.

In a corresponding manner, a second pressure sensor 122 for detecting the pressure in the second storage element 22 is provided. The second pressure sensor 122 is likewise connected to the electronic control unit 124 via a second sensor line 123.

For exchanging the data with other control devices connected to the vehicle electronics, an interface 126 is provided. Via the interface 126, the electronic control unit 124 may be connected to a CAN bus, for example. In the illustrated embodiment, the electronic control unit 124 is connected to the CAN bus represented by the interface 126 via further signal lines 127 and 128. About these other signal lines 127 and 128 z. B. the first controller 124 of the drive 1 '' information about a target speed v _3O n and an actual speed Vi _St supply. Depending on the ratio of the Solll speed v _so n and the actual speed Vi _at can then be made by the electronic control unit 124, the adjustment of the pivot angle of the hydraulic pump 9 and / or the hydraulic motor 12. Thus, an adaptation of the

Translation ratio in the hydraulic power branch to the required braking torque done. Furthermore, the control of the drive motor 2 is also involved in the electronic control by the electronic control unit 124. The drive motor 2 is controlled by an engine control unit 129. The engine control unit 129 is, for example, in connection with an injection pump, so that due to the setting of the engine control unit 129 an injection quantity for the drive motor 2 is metered.

The engine control unit 129 is connected via a

Engine control signal line 130 to the electronic control unit 124 and an information signal line 132 to the interface 126 in conjunction.

The electronic control unit 124 is further connected via a switching line 133 to the optional clutch 31. With the help of the switching line 133, for example, an actuator of the clutch 31 can be controlled. Such an actuator may, for. B. be designed as an electromagnet.

The electronic control unit 124 is connected to a first adjusting device 136 or a second adjusting device 137 via further control signal lines 134 and 135. The first adjusting device 136 acts on a

Adjusting mechanism of the hydraulic pump 9. Accordingly, the second adjusting device 137 acts on an adjusting mechanism of the hydraulic pump 12. In addition to the control of the adjusting devices 136, 137, a third control signal line 138 is provided, which acts on the valve block 23 with a control signal and thus the connection between the first working line 10th and the second working line 11 with the High-pressure accumulator line 26 and the low-pressure accumulator line 27 controls.

In the drive according to the invention with a power split transmission, it is preferred if the drive motor 2 is switched off during a braking operation. With the aid of the first pressure sensor 120 and the second pressure sensor 121, a memory state of the high-pressure accumulator, that is to say the first memory element 21, is determined which is sufficient

Having pressure energy to then safely start the drive motor 2 can. For this purpose, in the simplest case, only the pressure value determined by the first pressure sensor 120 in the first storage element 21 is compared with a first pressure limit value. If the pressure in the first storage element 21 exceeds this pressure limit value, the drive motor 2 is switched off by the electronic control unit 124 and the engine control unit 129 driven thereby.

To restart the drive motor 2, the stored pressure energy is also determined from at least the signal of the first pressure sensor 120. Preferably, the pressure difference between the pressure signal of the first pressure sensor 120 and the second pressure sensor 122 is considered

Basis for the determination of a sufficient pressure energy used. If the available pressure energy for starting the drive motor 2 falls below a second limit value, the drive motor 2 is automatically restarted. For this purpose, the electronic control unit 124 transmits a start signal to the clutch 31 or its actuator, so that the drive motor 2 is mechanically connected to the hydraulic pump 9. For starting the drive motor 2, the valve block 23 is then actuated via the signal line 138, that the pressure available in the first storage element 21 pressurizes the hydraulic pump 9. As a result, the hydraulic pump 9 acts as a hydraulic motor and generates an output torque with which the drive motor 2 is started.

During a braking operation, the first

Adjustment device 136 and the second adjusting device 137 in response to a specification of the electronic control unit 124 driven. Thus, during the braking operation, both the hydraulic pump 9 and the hydraulic motor 12 can be used to store pressure energy in the first storage element 21. Thus, the hydraulic motor 12 can be used together with the hydraulic pump 9 or only the hydraulic motor 12 or only the hydraulic pump 9 for storing pressure energy. In this case, in particular, the hydraulic pump 9 can be set to vanishing delivery volume and at the same time the clutch 31 are opened. Thus, all of the kinetic energy released by the braking process is stored by the hydraulic pump 12 in the first storage element 21.

The first storage element 21 is shown in the embodiments as a single hydraulic accumulator. However, it is also conceivable to provide a plurality of, for example, parallel memory elements. For all embodiments shown in the figures, it should be noted that both the two power branches, so the hydraulic

Power branch with the hydraulic pump 9 and the associated therein in the closed circuit hydraulic motor 12, together with the mechanical power branch and both power branches separately and independently can be operated. In particular, it should be noted that a larger transmission ratio can be achieved if, in addition to the two planetary gears already shown for example in FIG. 2 and FIG. 7, a third planetary gear stage is provided.

Of course, the control components, which are shown in Fig. 7 in connection with the embodiment of the drive 1 'of Fig. 2 are also transferable to the other drives.

The invention is not limited to the illustrated embodiments. In particular, combinations of individual aspects of the individual embodiments are possible in any way.

Claims

claims

1. drive with a power split transmission (1) comprising a hydraulic pump (9) and a via a first working line (10) and a second working line (11) associated therewith hydraulic motor (12), characterized in that at least a first memory element ( 21) for storing braking energy with the first working line (10) or the second working line (11) is connectable and that the hydraulic pump (9) and the hydraulic motor (12) are mechanically connected to an output shaft (18).

2. Drive according to claim 1, characterized in that the power split transmission (1) comprises at least one planetary gear (13) and the hydraulic motor (12) having an element and the hydraulic pump (9) is connected to another element of the planetary gear (13).

3. Drive according to claim 1 or 2, characterized in that the power take-off transmission has a mechanical power branch and a hydraulic power branch, wherein a torque transmission is possible both via one of the power branches and both power branches.

4. Drive according to one of claims 1 to 3, characterized in that the power split transmission (1) by a drive motor (2) is drivable and the drive motor (2) by means of a clutch (31) can be disengaged from the power split transmission.

A drive according to any of claims 1 to 4, characterized in that the power split transmission (1) comprises a first planetary gear (13) and a first drive shaft section (5.1) connected to the hydraulic pump (9) and a second connected to the first planetary gear (13) Drive shaft section (5.2) and the first drive shaft section (5.1) with the second drive shaft section (5.2) is detachably connectable.

6. Drive according to claim 4, characterized in that the power split transmission (1) comprises a second planetary gear (15) whose sun gear (31) is also connected to the second drive shaft section (5.2) and whose ring gear (33) with the ring gear (15 ) of the first planetary gear (13) is connected.

7. Drive according to claim 5 or 6, characterized in that the first drive shaft section (5.1) and the second drive shaft section (5.2) via at least one gear stage (38, 39) are vebindbar with each other.

8. Drive according to claim 6 or 7, characterized in that the web (35) of the second planetary gear (32) is blockable.

9. Drive according to one of claims 5 to 8, characterized the web (16) of the first planetary gear (13) is connected to an output shaft (18) of the power split transmission (1).

10. Drive according to one of claims 1 to 9, characterized in that the drive has a second storage element (22) which in at one of the two working lines (10, 11) connected to the first storage element (21) with the respective other working line (11 , 10).

11. Drive according to one of claims 1 to 10, d characterized in that during a braking operation and above a

Pressure limit value in the first storage element (21) of the drive motor (2) is switched off.